Why does a cost of living increase in my social security of $14.00/mo. translate into an increase of $30.00/Mo in my health care billing due to a reduction of my subsidy?
Social Security benefits count toward household income for the purposes of tax credits, so if you claim more SS tax credits go down, claim less and they go up. If your Social Security benefits are adjusted mid-year make sure to update the Marketplace so tax credits can be adjusted. This will avoid you haven't to pay back excess tax credits up to the repayment limit.
Non-taxable Social Security benefits(1) (Line 20a minus 20b on a Form 1040) “Social Security benefits” includes disability payments (SSDI), but does not include Supplemental Security Income (SSI) (which should be excluded).